Engine Operation in Flight for Minimum Fuel Consumption

Description:

Engine and airplane performance data have been gathered from various sources and analyzed to determine indications of the most economical methods of flight operation from a consideration of fuel expenditure. The analysis includes the influence of such facts as fuel-air ratio, engine speed, engine knock, altitude, cylinder cooling, spark timing, and limits of cruising brake mean effective pressure. The results indicate that the cheapest power is obtained with approximately correct mixture at low engine speed and highest permissible manifold pressure. If more power is desired, the methods of obtaining it are, in order of fuel economy: (a) increasing the engine speed and maintaining safe cylinder temperatures by cooling; (b) retarding the spark or cooling further to permit higher manifold pressure; and, (c) riching the mixture. The analysis further shows that the maximum time endurance of flight occurs at the air speed corresponding to minimum thrust horsepower required and with minimum practicable engine speed. Maximum mileage per pound of fuel is obtained at slightly higher air speed. The fuel-air ratio should be approximately the theoretically correct ratio in both cases. For an engine equipped with a geared supercharger, as in the example presented, and with knock as the limiting condition, a comparison of operation at sea level and at 6,000 feet shoes flight at altitude to be more economical on the basis of both range and endurance.

Creator(s): Reuter, George
Creation Date: November 1, 1939
Partner(s):
UNT Libraries Government Documents Department
Collection(s):
National Advisory Committee for Aeronautics Collection
Technical Report Archive and Image Library
Usage:
Total Uses: 43
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Creator (Author):
Date(s):
  • Creation: November 1, 1939
Description:

Engine and airplane performance data have been gathered from various sources and analyzed to determine indications of the most economical methods of flight operation from a consideration of fuel expenditure. The analysis includes the influence of such facts as fuel-air ratio, engine speed, engine knock, altitude, cylinder cooling, spark timing, and limits of cruising brake mean effective pressure. The results indicate that the cheapest power is obtained with approximately correct mixture at low engine speed and highest permissible manifold pressure. If more power is desired, the methods of obtaining it are, in order of fuel economy: (a) increasing the engine speed and maintaining safe cylinder temperatures by cooling; (b) retarding the spark or cooling further to permit higher manifold pressure; and, (c) riching the mixture. The analysis further shows that the maximum time endurance of flight occurs at the air speed corresponding to minimum thrust horsepower required and with minimum practicable engine speed. Maximum mileage per pound of fuel is obtained at slightly higher air speed. The fuel-air ratio should be approximately the theoretically correct ratio in both cases. For an engine equipped with a geared supercharger, as in the example presented, and with knock as the limiting condition, a comparison of operation at sea level and at 6,000 feet shoes flight at altitude to be more economical on the basis of both range and endurance.

Language(s):
Subject(s):
Keyword(s): aircraft propulsion and power
Contributor(s):
Serial Title: NACA Special Report
Partner:
UNT Libraries Government Documents Department
Collection:
National Advisory Committee for Aeronautics Collection
Collection:
Technical Report Archive and Image Library
Identifier:
Resource Type: Report
Format: Text
Rights:
Access: Public
Statement: No Copyright, Unclassified, Unlimited, Publicly available